Two cases of COVID-19 have been confirmed in staff members at a Melbourne aged care home, one week after a resident was diagnosed with the virus and the facility went into lockdown.
The two diagnoses take the total number of cases at Lynden Aged Care in Camberwell to three.
The facility went into lockdown on May 19 after a resident was diagnosed with the virus.
The Department of Health and Human Services (DHHS) said the source of the latest infections was under investigation.
But the new cases were not identified as close contacts of the first case so the two staff members continued to work at the facility.
Staff members identified as close contacts of the two new cases have been placed into quarantine.
Residents and families were being notified, the health department said.
All staff and residents were tested after the notification of the first case and a further round of testing is underway.
'Odd and unusual' test results at Caulfield aged care facility
It comes as an aged care home in Melbourne's south-east is investigating why two of its residents have returned conflicting coronavirus test results this month.
Victoria recorded five new coronavirus cases since Monday, one of whom is a resident at the HammondCare aged care facility in Caulfield.
In a statement, HammondCare said while the resident had returned a positive result on the first test, the second test result was negative.
HammondCare said the first resident, who was not unwell, was in a separate cottage to the resident who tested positive this week.
In both instances, health authorities and the care home have treated the cases as outbreaks and gone into lockdown, isolated the resident who returned the positive results and sent close contacts into self-quarantine.
"We share your concerns and understand if you have found this experience confusing and frustrating," HammondCare's senior nurse Angela Raguz said in a letter to residents and families.
"We certainly acknowledge that this circumstance is odd and unusual."
Ms Raguz said HammondCare was working with the Department of Health and Human Services (DHHS) to understand why the conflicting results had occurred.
Tests may have picked up a different coronavirus strain
Victoria's Chief Health Officer Brett Sutton said one possible explanation for the test results was that some labs were detecting different strains of coronavirus, those which did not cause COVID-19.
"It can be a bit unusual, and sometimes the tests have been done at a lab that has a slightly different methodology that might be likely to pick up a … reaction with another coronavirus," he told ABC Radio Melbourne.
"That's uncommon, but when you're doing 10,000 tests a day that will happen occasionally."
When asked whether residents should be physically removed from aged care homes in the event of a positive case to avoid an outbreak, Professor Sutton said by putting the homes into lockdown and securing test results for "absolutely everyone within that setting" within 24 hours, the risk was reasonably well managed already.
"I think it can be highly disruptive if you were to move out a number of people, so I think it's reasonable to do that very broad testing while it's in lockdown, get those results back," he said.
Speaking more broadly, Professor Sutton said it was possible Victoria could be in a position where there were zero cases of community transmission within a few weeks, but he said cases in overseas arrivals in quarantine would continue.
When asked about reports of some Victorians waiting up to 10 days for coronavirus test results, he said he was "concerned" by the idea that infected Victorians might stop quarantining out of impatience and spread the virus.
He said some private labs were struggling with the demand more than others.
"But we're working with each and every one of those private labs to understand where their constraints are," he said.
Three of the state's five new cases announced on Tuesday were returned overseas travellers in hotel quarantine, while the other infected person was detected through community testing and was not linked to any known outbreak.
The state's biggest outbreak at the Cedar Meats Australia abattoir in Melbourne's west remains at 111 cases, with no new cases linked to the cluster since Friday.
